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Topics - m.slaterpfl

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Character LCDs / NHD-0420DZW-AY5 Display Disapears
« on: April 28, 2017, 09:23:01 AM »
Hello,

The manufacturers of a product we designed which uses the NHD-0420DZW-AY5 display sent us a few units back which they said didn't work so I have been busy trying to repair them.

I have managed to fix all but one which is acting very strange.

When using a simple "Hello World" program the text initially displays but then fades away within a second of setting the text. After this has happened either power cycling the screen or trying to refresh the text have no effect and the display stays blank. The supply voltage has to be removed for a minute or so before the text will display and fade again. Because of this behaviour it feels like a capacitor might be faulty somewhere but without a schematic I wouldn't know where to begin trying to replace them. The display is still drawing about 30 mA at 3.3V after it has faded away.

Do you think it is one of the SMD devices on the back that is faulty and could be replaced or is the whole unit a write off?

Thanks,
Michael.

(Some specifics)
It is a Revision A display
Powered with 3.3V from a bench supply
All jumpers are set to the serial interface as per the data sheet
The test circuit and code work with other displays
The correct text is displayed, it just fades to black in less than a second.

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